Why Mikrotik RouterOS/RouterBoard?
LR2 base station could be installed in any part of network. The protocols IPsec, PPPoE, PPPTP are easily suitable for access area and protocols MPLS, OSPF, BGP for backhaul area. RouterOS allows covering a complete networking stack as well as firewall and src/dst NAT and much more.
Why to use SPI, rather then USB?
Semtech removed USB support from official Driver/HAL since version 3.2.0 due lack of performances. Only SPI usage is supported in the new versions of official Semtech driver/HAL (https://github.com/Lora-net/lora_gateway).
Ansible (https://github.com/ansible) is one of the most widespread tool for a massive central management of the IT infrastructure. Ansible along with ansible-semaphore (https://github.com/ansible-semaphore/semaphore) is the ideal set of tools for a complex management of widespread LR2 infrastructure.